In-wheel driving inverter inside engine room sometimes operates in the harsh environment like high temperature of about $105^{circ}C$. Especially, the size and power density of the inverter has become smaller and more increased. Thus, it is essential to manage the temperature of the inverter with IGBT (Insulated Gate Bipolar Transistor) switching devices for performance and endurance, because the temperature can be getting increase. In this paper, we performed the thermal flow analysis of inverter models with wave type and pin fin type cooling channels, and investigated the heat transfer characteristics of the inverter models using cooling water on channels at 8 L/min and $65^{circ}C$. Also, we compared the thermal performance under various conditions such as coolant flow rate and layered power module structure. Therefore, we determined the feasibility of the initial inverter models and the thermal performance enhancement.